Golf Ball Having Temperature Controllable Compression Deformation

ABSTRACT

A golf ball having a cover layer, an outer core layer, and an inner core layer. The inner core layer has a first compression deformation at 24° C. and a second compression deformation at 70° C. The ratio between the second compression deformation and the first compression deformation is between approximately 1.5 and approximately 2.5.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/513,168, entitled “Golf Ball Having Temperature Controllable Compression Deformation,” and filed on Jul. 29, 2011, which application is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates generally to a golf ball having an inner core layer with certain compression deformation characteristics and, more particularly, to a golf ball having an inner core layer with temperature controllable compression deformation.

BACKGROUND

A golfer typically selects a golf ball that has a combination of features based on his or her preferences and/or skill. Golf ball designers often attempt to provide a ball with characteristics that are balanced to suit a variety of golfer preferences and/or skill. Frequently, golf balls include a plurality of layers, with each layer helping to provide one or more desired qualities.

In some cases, a golfer may select a golf ball having a particular compression or compression deformation according to their preference, skill, and/or swing characteristics. For example, golf balls having a higher compression deformation may be preferred and/or suited for use by golfers having a swing with relatively higher club head speed. Matching the compression deformation and the golfer's club head speed can often optimize, or otherwise improve, the golfer's driving distance. In some cases, golfers with slower swing speeds may choose a more compressible ball (that is, with a higher compression deformation) while a golfer with a faster swing speed may choose a less compressible ball (that is, with a lower compression deformation). In addition, it is common for a golfer to wish to try golf balls of different compression deformation values to determine which type of ball best suits his skills and/or preference. In order to try golf balls of different compression deformation, the golfer may need to purchase multiple different balls, each with a different compression deformation value. This type of trial-and-error ball fitting can be expensive and inefficient.

Heating systems have been developed that golfers may use before playing to heat a ball to a certain temperature in order to achieve certain modified performance characteristics. However, as the player plays and time passes, the ball cools and the modified performance characteristics may revert substantially back to the pre-heated levels before the player has completed a round of golf. It would be desirable to provide a ball with thermally-modifiable compression deformation. It would also be desirable to provide a ball that may maintain a modified compression deformation for a sustained amount of time in order to enable a golfer to complete a round using the modified compression deformation.

The present disclosure is directed to improvements in customizability of golf ball performance characteristics.

SUMMARY

In one aspect, the present disclosure is directed to a golf ball including a cover layer, an outer core layer disposed radially inward of the cover layer, and an inner core layer disposed radially inward of the outer core layer. The inner core layer may have a first compression deformation at 24° C. and a second compression deformation at 70° C., wherein a first ratio between the second compression deformation and the first compression deformation is between approximately 1.5 and approximately 2.5.

In another aspect, the present disclosure is directed to a golf ball including a cover layer, an outer core layer disposed radially inward of the cover layer, and an inner core layer disposed radially inward of the outer core layer. The inner core layer may have a first compression deformation at 24° C., a second compression deformation after heating to 70° C., and a third compression deformation after cooling at 24° C. for 90 minutes. The ratio between the third compression deformation and the first compression deformation may be between approximately 1.08 and approximately 1.35.

In another aspect, the present disclosure is directed to a golf ball including a cover layer, an outer core layer disposed radially inward of the cover layer, and an inner core layer disposed radially inward of the outer core layer. The inner core layer may have a first compression deformation at 24° C., a second compression deformation after heating to 70° C., and a fourth compression deformation after cooling at 24° C. for 150 minutes. The ratio between the fourth compression deformation and the first compression deformation may be between approximately 1.08 and approximately 1.35.

In another aspect, the present disclosure is directed to a golf ball including a cover layer, an outer core layer disposed radially inward of the cover layer, and an inner core layer disposed radially inward of the outer core layer. The inner core layer may have a first compression deformation at 24° C., a second compression deformation after heating to 70° C., and a fifth compression deformation after cooling at 24° C. for 210 minutes. The ratio between the fifth compression deformation and the first compression deformation may be between approximately 1.08 and approximately 1.35.

Other systems, methods, features and advantages of the invention will be, or will become, apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description and this summary, be within the scope of the invention, and be protected by the following claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views.

FIG. 1 shows a cutaway, partial cross-sectional view of an exemplary golf ball in accordance with this disclosure, the golf ball being of a three-piece construction; and

FIG. 2 shows a cutaway, partial cross-sectional view of an exemplary golf ball, having a four-piece construction.

DETAILED DESCRIPTION

The present disclosure is directed to a golf ball formed of materials and layers with certain performance characteristics. The following paragraphs explain the measurement processes for several characteristics.

For purposes of this disclosure, the term “compression deformation” refers to the amount deformation exhibited by an object when compressed under a predetermined set of loading parameters. As used in the present disclosure, compression deformation shall refer to the deformation amount (in millimeters) of an object when compressed by a force, specifically, the deformation of the object when the compression force is increased from 10 kg to 130 kg. The deformation amount of the object under the force of 10 kg is subtracted from the deformation amount of the object under the force of 130 kg to obtain the compression deformation value of the object. While compression deformation is a parameter that may be measured for entire golf balls, compression deformation can also be measured for individual components of golf balls. In the present disclosure, compression deformation of a golf ball inner core layer, which, like the entire golf ball, may be also be spherical, is measured and discussed in detail.

Hardness of a golf ball layer is measured generally in accordance with ASTM D-2240. In some cases the hardness may be measured on a cross-sectional surface of a ball layer. In other cases, the hardness may be measured on the curved surface of a ball layer.

Coefficient of restitution (COR), as referred to in the present disclosure, is measured in the following manner. To measure COR, a golf ball is fired by an air cannon, or other propulsion device, at an initial velocity of 40 m/sec toward a steel plate located about 1.2 meters away from the cannon. A speed monitoring device is located at a distance of 0.6 to 0.9 meters from the cannon. The speed monitoring device measures the speed of the golf ball after bouncing off the steel plate. The return velocity divided by the initial velocity is the COR.

The present disclosure is directed to golf ball layers having certain performance characteristics. These characteristics may be achieved due to the structural configuration of the layers and/or the material compositions of the layers. Further, the overall performance characteristics of the golf ball are affected in certain ways by the makeup of individual layers and also reflect the combination and arrangement of the layers and materials from which the golf ball is formed. The concepts discussed in the present disclosure may be applicable to golf balls having any construction, having any suitable number of layers. In some embodiments, an exemplary golf ball having the disclosed performance characteristics may have a three-piece or -layer construction. In other embodiments, the ball may have a four-piece construction. In addition, other configurations are envisioned that include five or more layers.

Further, although the disclosure describes various embodiments relating to golf balls, a person having ordinary skill in the art will be able to adapt the disclosed concepts for use in other types of balls (other than golf balls) and for use in other types of layered articles. For example, the disclosed concepts may be applicable to any layered article, such as a projectile, ball, recreational device, or individual components of these articles.

FIG. 1 illustrates a cutaway, partial cross-sectional view of an exemplary three-piece golf ball construction. As shown in FIG. 1, a golf ball 100 may include a cover layer 105, an outer core layer 110 disposed radially inward of cover layer 105, and an inner core layer 105 disposed radially inward of outer core layer 110. The dimensions and materials of each layer may be selected to achieve desired performance characteristics.

Cover layer 105 may be formed of a relatively soft but durable material. For example, cover layer 105 may be formed of a material that compresses/flexes when struck by a golf club, in order to provide spin of the ball and feel to the player. Although relatively soft, the material may also be durable, in order to withstand scuffing from the club and/or the golf course. Exemplary cover layer materials may include urethane, ionomer blends, or any other suitable material, including blends.

In addition, FIG. 1 illustrates the outer surface of cover layer 105 as having a generic dimple pattern. While the dimple pattern on golf ball 100 may affect the flight path of golf ball 100, any suitable dimple pattern may be used with the disclosed embodiments. In some embodiments, golf ball 100 may be provided with a dimple pattern including a total number of dimples between approximately 300 and 400.

Outer core layer 110 may be formed of a relatively firm and suitably resilient material. Outer core layer 110 may be configured to provide a relatively high launch and a relatively low spin rate when the ball is struck by a driver, and a relatively higher spin rate and increased control when struck with irons. This may provide distance off the tee with spin and control around the greens.

Inner core layer 115 may be formed of a relatively firm material, such as hard rubber, in order to provide distance. The thickness of the golf ball layers may be varied in order to achieve desired performance characteristics. In some embodiments, inner core layer 115 may be spherical with a diameter 120 of between approximately 21 mm and approximately 30 mm, more typically between approximately 24 mm and approximately 28 mm.

While the disclosed concepts may be applicable to three-piece golf balls, such as golf ball 100, for purposes of discussion, the disclosed concepts will be discussed in greater detail below with respect to a four-piece golf ball construction. It will be understood, however, that the concepts discussed below are applicable to golf balls having a three-piece construction, four-piece construction, five-piece construction, or any other suitable configuration.

FIG. 2 is a cutaway, partial cross-sectional view of a golf ball 200 having a four-piece construction. As shown in FIG. 2, golf ball 200 may have four layers that are positioned adjacent one another. For example, in some embodiments, golf ball 200 may include an outer cover layer 205 and an inner cover layer 210 disposed radially inward of outer cover layer 205. Golf ball 200 may also include an outer core layer 215 disposed radially inward of inner cover layer 210, and an inner core layer 220 disposed radially inward of outer core layer 215. Any layer may surround or substantially surround any layers disposed radially inward of that layer. For example, outer core layer 215 may surround or substantially surround inner core layer 220.

In the present disclosure and drawings, golf ball 200 is described and illustrated as having four layers. In some embodiments, at least one additional layer may be added. For example, in some embodiments, a mantle layer may be added between outer core layer 215 and inner cover layer 210. In some embodiments, an intermediate cover layer may be inserted between inner cover layer 210 and outer cover layer 205. Further, in some embodiments, an intermediate core layer may be inserted between inner core layer 220 and outer core layer 215. Other layers may be added on either side of any disclosed layer as desired to achieve certain performance characteristics and/or attributes.

In some embodiments, golf ball 200 may have a diameter of at least 42.67 mm (1.680 inches), in accordance with the Rules of Golf. For example, in some embodiments, golf ball 200 may have a ball diameter between about 42.67 mm and about 42.9 mm, and may, in some embodiments, have a ball diameter of about 42.7 mm. Golf ball 200 may have a ball weight between about 45 g and about 45.8 g and may, in some embodiments, have a ball weight of about 45.4 g. The golf ball may be ‘conforming,’ i.e., in conformance with the USGA rules about golf balls, including weight, diameter, initial velocity, and the like, or it may be ‘non-conforming.’

In some embodiments, outer core layer 215 may have a thickness of at least about 5 mm. In some embodiments, inner core layer 220 may be a sphere having a diameter 225 in the range of approximately 21 mm to 30 mm. In some embodiments, diameter 225 of inner core layer 220 may be in the range of approximately 24 mm to 28 mm. For example, in some embodiments, diameter 225 may be 24 mm. In other embodiments, diameter 225 may be 28 mm.

One parameter that can have an affect on the performance of the ball is the compression deformation. Compression deformation is a physical parameter that may be quantified (in millimeters for example) according to the measurement protocol set forth above. A higher compression deformation value indicates that the ball deforms more when subjected to a given compressive force. That is, a ball having a higher compression deformation is more compressible than a ball having a lower compression deformation.

In one embodiment of the invention, the inner core layer has a first compression deformation of between about 3 mm and about 5 mm at 24° C., a second compression deformation of between about 6 mm to about 8 mm, and a third compression deformation of between about 3.5 mm and about 5.5 mm after cooling at 24° C. for 90 minutes. A first ratio between the second compression deformation and the first compression deformation is between about 1.5 and about 2.5, more typically between approximately 1.80 and approximately 2.14, and a second ratio between the third compression deformation and the first compression deformation typically is between approximately 1.08 and approximately 1.35, more typically between approximately 1.13 and approximately 1.33.

In embodiment of the invention, the inner core layer of a golf ball has a fourth compression deformation after cooling at 24° C. for 150 minutes. The ratio between the fourth compression deformation and the first compression deformation may be between approximately 1.08 and approximately 1.35, and more typically between approximately 1.11 and approximately 1.26.

In still another embodiment of the invention, the golf ball includes an inner core layer having a fifth compression deformation after cooling at 24° C. for 210 minutes. The ratio between the fifth compression deformation and the first compression deformation is between approximately 1.08 and approximately 1.35, more typically between approximately 1.09 and 1.19.

Inner Core Layer

The overall compression deformation characteristics of the ball as a whole may be determined by the combined effect of the layers. However, certain layers may be developed to provide a higher or lower compression deformation. In some cases the compressibility of the inner core layer may have a significant effect on the overall compression deformation of the ball. In some embodiments, the compression deformation of the inner core layer may be changed to alter the performance characteristics of the ball. Further, in some embodiments, the changed characteristics may be sustainable over an extended period of time.

Changes in compression deformation of the inner core layer may be effectuated by heating the ball. For example, the inner core layer may exhibit an increase in compression deformation when heated. Therefore, by controlling the range of compression deformation among different temperature stages, one can achieve different compression deformation values with the same ball. Accordingly, different balls need not be purchased in order to enable one to play with different compression deformation values, since different compression deformation values can be achieved with a single ball by, for example, applying different amounts of heat to it.

In order to provide greater changes in compression deformation, the golf ball may include a thermoplastic inner core layer. The extent to which the compression deformation value of an inner core layer may be altered may be significantly greater with a thermoplastic inner core layer than with a thermoset inner core layer. Further, the altered compression deformation characteristic may be sustained for a longer period of time, as well. Accordingly, while thermoset materials are commonly used for inner core layers, the present embodiments may implement a thermoplastic inner core layer in order to provide greater variability and sustainability of variations in compression deformation characteristics.

EXAMPLES

Inner core layer materials were tested for compression deformation. Table I provides the composition of two thermoset materials from which an inner core layer was formed. Table II lists a thermoplastic material from which an inner core layer was formed.

TABLE I Thermoset Inner Core Layer Materials Rubber Compound Material A Material B TAIPOL BR0150* 100 100 Zinc diacrylate 19 21 Zinc oxide 6 6 Barium sulfate 20 18 Peroxide 1 1 *TAIPOL BR0150 is the trade name of rubber by Taiwan Synthetic Rubber Corp.

TABLE II Thermoplastic Inner Core Layer Material Resin Material C HPF AD1035* 100 *HPF AD1035 is trade name of ionomeric resin by E. I. DuPont de Nemours and Company

Table III includes compression deformation data for sample inner core layers formed of Materials A, B, and C. Four inner core layers, numbered 1-4 in Table III, were formed. Core 1 is a 24 mm core of Material C, and Cores 2, 3, and 4 are 28 mm cores made of Material C, Material B, and Material A, respectively. To obtain the data in Table III, the compression deformation of each core was determined at 24° C. (“Test “A”). Then each core was heated for two hours at 70° C., and the compression deformation of each heated core at 70° C. was determined (“Test “B”). After heating, each core then was cooled in a 24° C. atmosphere. The compression deformation of each core was determined again after 90 minutes (“Test “C”), 150 minutes (“Test “D”), and 210 minutes (“Test “E”) in the 24° C. environment.

Determinations were carried out on two Comparative Examples, Cores 3 and 4, and on 2 highly neutralized acid polymer cores (1 and 2). The cores were evaluated for compression deformation at the temperatures identified; these compression deformation values are set forth in the columns marked “Test A” through “Test E” in Table III below. The ratios of compression deformation values at the various temperatures were calculated, and are set forth in Table III. This testing simulates the cooling of a heated ball over time during the course of play.

TABLE III Core Material and Compression Deformation (mm) Compression Deformation Ratios No. Diameter Test A Test B Test C Test D Test E B/A C/A D/A E/A 1 Material C: 3.49 7.47 4.63 4.41 4.16 2.14 1.33 1.26 1.19 24 mm 2 Material C: 3.52 6.33 3.98 3.92 3.84 1.80 1.13 1.11 1.09 28 mm 3 Material B: 3.92 4.50 4.08 3.96 3.97 1.15 1.04 1.01 1.01 28 mm 4 Material A: 4.21 4.67 4.33 4.31 4.3 1.11 1.03 1.02 1.02 28 mm

Compression Deformation (70° C. Alone)

Table III illustrates the capacity to modify the compression deformation value of a ball using both a comparative thermoset material and a thermoplastic material. The data and comparisons indicate that the thermoplastic inner core layer sustains a greater compression deformation ratio for a longer period.

In addition to providing compression deformation data, Table III also includes data regarding compression deformation ratios. Compression deformation ratios provide metrics by which the Cores 1 and 2 were compared to Cores 3 and 4. The ratio of the compression deformation value after heating to the value before heating provides an indication of the change in compressibility. In addition, compression ratios of the post cooling values to the pre-heating values (C/A, D/A, and E/A) provide an indication of the sustainability of any increases in compression deformation obtained by heating.

After heating to the atmospheric control temperature (24° C.), the compression deformation of each sample was tested (Test A). Then, each sample was heated in a 70° C. oven for two hours. After the 70° C. heating, the compression deformation of each sample was tested again (Test B). This testing of the compression deformation of the samples following 70° C. heating revealed that the thermoplastic inner core layers 1 and 2 exhibited greater increases in compression deformation due to heating than thermoset inner core layers 3 and 4.

As illustrated in Table III, Core 1 had an unheated (24° C.) compression deformation of 3.49 mm (Test A), and a heated (70° C.) compression deformation of 7.47 mm (Test B). Thus, the ratio of compression deformations of Test B/Test A was 2.14. Similarly, Core 2 had an unheated (24° C.) compression deformation of 3.52 mm, and a heated (70° C.) compression deformation of 6.33 mm, a B/A ratio of 1.80. In contrast, Cores 3 and 4 exhibited B/A ratios of 1.15 and 1.11, respectively. Thus, the compressibility of the two thermoplastic cores was increased to a significantly greater extent by the 70° C. heating than the two thermoset cores.

Compression Deformation (90 Min Cooled)

Core 1 had a compression deformation after cooling for 90 minutes of 4.63 mm (Test C), and thus, a compression deformation ratio (Test C/Test A) of 1.33. Similarly, Core 2 had a compression deformation after 90 minutes of cooling (Test C) of 3.98 mm, and thus, a C/A compression deformation ratio of 1.13. In contrast, Cores 3 and 4 demonstrated C/A compression deformation ratios of 1.04 and 1.03 respectively.

As illustrated in Table III and discussed above, the thermoplastic material samples sustain an increased level of compressibility significantly longer than the thermoset material samples. It may be possible to play a round of nine holes in approximately 90 minutes. Accordingly, the data above regarding the properties of thermoplastic inner core layers after 90 minutes of cooling (following 70° C. heating) indicates the sustainability of increased compression deformation values through at least a round of nine holes.

Compression Deformation (150 Minutes Cooled)

Core 1 had a compression deformation of 4.41 mm after cooling for 150 minutes (Test D), and thus, a compression deformation ratio (Test D/Test A) of 1.26. Similarly, after 150 minutes of cooling (Test D), core 2 yielded a compression deformation of 3.92 mm, and thus, a D/A compression deformation ratio of 1.11. In contrast, the comparative cores 3 and 4 demonstrated D/A compression deformation ratios of 1.01 and 1.02 respectively.

As shown in Table III and discussed above, at the extended period of 150 minutes after heating, the thermoplastic material samples continued to sustain an increased level of compressibility over the thermoset material samples. It may be possible to play a relatively slow, or otherwise delayed, round of nine holes, or a relatively fast round of 18 holes in approximately 150 minutes. Accordingly, the data above regarding the properties of thermoplastic inner core layers after 150 minutes of cooling (following 70° C. heating) indicates the sustainability of increased compression deformation values through at least a round of nine holes, and possibly a round of 18 holes.

Compression Deformation (210 Minutes Cooled)

Cores 1 and 2 yielded compression deformations of 4.16 mm and 3.84 mm, respectively, after cooling for 210 minutes, and thus, a compression deformation ratio (Test E/Test A) of 1.19. In contrast, Cores 3 and 4, the comparative examples, demonstrated E/A compression deformation ratios of 1.01 and 1.02 respectively.

As shown in Table III and discussed above, at the further extended time point of 210 minutes after heating, the thermoplastic material samples still continued to sustain an increased level of compressibility over the thermoset material samples. It may be possible to play a round of 18 holes in approximately 210 minutes. Accordingly, the data above regarding the properties of thermoplastic inner core layers after 210 minutes of cooling (following 70° C. heating) indicates the sustainability of increased compression deformation values through a round of 18 holes.

Other Properties of Inner Core Layer

In addition to compression deformation, other properties may be desirable for the inner core layer. For example, it may be desirable for the inner core layer to have a certain hardness and/or specific gravity.

In some embodiments, inner core layer 220 may have a surface Shore D hardness in the range of about 45 to 55. To provide golf ball 200 with stable performance, inner core layer 220 may have a Shore D cross-sectional hardness of from 45 to 55 at any single point on a cross-section obtained by cutting inner core layer 220 in half. Further, inner core layer 220 may have a Shore D cross-sectional hardness difference between any two points on the cross-section of within +/−6 and, in some embodiments, the difference between any two points on the cross-section may be within +/−3.

Certain performance characteristics of the golf ball, such as moment of inertia, may be determined, in part, by the comparative physical properties of the different layers of the golf ball. For example, in some embodiments, a greater moment of inertia may be achieved by forming layers disposed radially outward from the center of the ball with a higher specific gravity, and by forming layers disposed radially inward toward the center of the ball with a relatively lower specific gravity. A golf ball with a greater moment of inertia may maintain its rate of spin for longer than a golf ball with a lower moment of inertia. This may provide a ball with improved short game characteristics, as spin enables a player to hit a ball near the hole with limited roll beyond the point of impact and, in some cases, even roll backward after landing. Spin may also contribute to longer drives, as the trajectory will not drop off as steeply as the ball starts coming back down after reaching its apex.

In some embodiments, it may be desirable for golf ball 200 to have a moment of inertia between about 82 g-cm² and about 90 g-cm². Such a moment of inertia may produce desirable distance, trajectory, and control. Such a moment of inertial may produce desirable performance characteristics, for example, when golf ball 200 is struck with a driver and/or is flying against the wind. To provide golf ball 200 with a greater moment of inertia, inner core layer 220 may have a lower specific gravity than outer layers. In some embodiments, the specific gravity of inner core layer 220 may be in the range of about 0.9 g/cm³ to about 1.1 g/cm³.

Materials of Inner Core Layer

In some embodiments, inner core layer 220 may be formed, at least in part, from a highly neutralized acid polymer. The acid polymer may be neutralized to 80% or higher, including up to 100%, with a suitable cation source, such as magnesium, sodium, zinc, or potassium. Suitable highly neutralized acid polymers for use in forming inner core layer 220 may include a highly neutralized acid polymer and optionally additives, fillers, and/or melt flow modifiers.

Suitable additives and fillers may include, for example, blowing and foaming agents, optical brighteners, coloring agents, fluorescent agents, whitening agents, UV absorbers, light stabilizers, defoaming agents, processing aids, antioxidants, stabilizers, softening agents, fragrance components, plasticizers, impact modifiers, acid copolymer wax, and surfactants. In some embodiments, the additives and fillers may include, for example, inorganic fillers, such as zinc oxide, titanium dioxide, tin oxide, calcium oxide, magnesium oxide, barium sulfate, zinc sulfate, calcium carbonate, zinc carbonate, barium carbonate, mica, talc, clay, silica, lead silicate, and other types of organic fillers. In some embodiments, the additives and fillers may include, for example, high specific gravity metal powder fillers, such as tungsten powder, molybdenum powder, and others. In some embodiments the additives and fillers may include regrind, that is, core material that is ground and recycled.

Any suitable melt flow modifiers may be included in the highly neutralized acid polymer. Exemplary suitable melt flow modifiers may include, for example, fatty acids and salts thereof, polyamides, polyesters, polyacrylates, polyurethanes, polyethers, polyureas, polyhydric alcohols, and combinations thereof.

Exemplary highly neutralized acid polymers suitable for forming inner core layer 220 may include, for example, HPF resins such as HPF1000, HPF2000, HPF AD1024, HPF AD1027, HPF AD1030, HPF AD1035, HPF AD1040, all produced by E.I. Dupont de Nemours and Company.

Inner core layer 220 may be formed by any suitable process, such as injection molding or compression molding. During an exemplary injection molding process of forming inner core layer 220, the temperature of the injection machine may be set in a range of approximately 190° C. to 220° C.

Outer Core Layer

Outer core layer 215 may have a thickness that is suitable to protect inner core layer 220. In some cases, after heating golf ball 200 to a temperature of approximately 70° C., inner core layer 220 may be sensitive to handling. Therefore, outer core layer 215 may be provided with a thickness that protects inner core layer 220 from post-heating handling. For example, in some embodiments, outer core layer 215 may have a thickness of at least 5 mm.

As with other layers, the hardness of outer core layer 215 may have an affect on the performance of ball 200. In some embodiments, it may be desirable for outer core layer 215 to have a surface hardness that is higher than the surface hardness of inner core layer 220. For example, in some embodiments, outer core layer 215 may have a surface Shore D hardness in the range of approximately 50 to 60.

Outer core layer 215 may be formed of a thermoset material. For example, in some embodiments, outer core layer 215 may be formed by crosslinking a polybutadiene rubber composition. When other rubber is used in combination with a polybutadiene, polybutadiene may be included as a principal component. For example, a proportion of polybutadiene in the entire base rubber may be equal to or greater than 50 percent by weight and, in some embodiments, may be equal to or greater than 80 percent by weight. In some embodiments, outer core layer 215 may be formed of a polybutadiene rubber composition including a polybutadiene having a proportion of cis-1,4 bonds of equal to or greater than 60 mol percent. For example, in some embodiments, the proportion may be equal to or greater than 80 mol percent.

In some embodiments, cis-1,4-polybutadiene may be used as the base rubber and mixed with other ingredients. In some embodiments, the amount of cis-1,4-polybutadiene may be at least 50 parts by weight, based on 100 parts by weight of the rubber compound. Various additives may be added to the base rubber to form a compound. The additives may include a cross-linking agent and a filler. In some embodiments, the cross-linking agent may be zinc diacrylate, magnesium acrylate, zinc methacrylate, or magnesium methacrylate. In some embodiments, zinc diacrylate may provide advantageous resilience properties.

In some embodiments, the filler may include zinc oxide, barium sulfate, calcium carbonate, or magnesium carbonate. In some embodiments, zinc oxide may be selected for its advantageous properties. In some embodiments, the filler may be used to increase the specific gravity of the material. For example, metal powder, such as tungsten, may alternatively be used as a filler to achieve a desired specific gravity. In some embodiments, the specific gravity of outer core layer 215 may be in the range of about 1.05 g/cm³ to about 1.35 g/cm³.

In some embodiments, a polybutadiene synthesized using a rare earth element catalyst is preferred. Using this polybutadiene may provide golf ball 200 with increased resilience. Examples of rare earth element catalysts include a lanthanum series rare earth element compound, an organoaluminum compound, an alumoxane, and a halogen containing compound. A lanthanum series rare earth element compound is preferred. Polybutadiene obtained by using lanthanum rare earth-based catalysts usually employ a combination of lanthanum rare earth (atomic number of 57 to 71) compounds, but particularly preferred is a neodymium compound.

In some embodiments, the polybutadiene rubber composition may comprise at least from about 0.5 parts by weight to about 5 parts by weight of a halogenated organosulfur compound. In some embodiments, the polybutadiene rubber composition may comprise at least from about 1 part by weight to about 4 parts by weight of a halogenated organosulfur compound. The halogenated organosulfur compound may be selected from the group consisting of pentachlorothiophenol; 2-chlorothiophenol; 3-chlorothiophenol; 4-chlorothiophenol; 2,3-chlorothiophenol; 2,4-chlorothiophenol; 3,4-chlorothiophenol; 3,5-chlorothiophenol; 2,3,4-chlorothiophenol; 3,4,5-chlorothiophenol; 2,3,4,5-tetrachlorothiophenol; 2,3,5,6-tetrachlorothiophenol; pentafluorothiophenol; 2-fluorothiophenol; 3-fluorothiophenol; 4-fluorothiophenol; 2,3-fluorothiophenol; 2,4-fluorothiophenol; 3,4-fluorothiophenol; 3,5-fluorothiophenol 2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol; 2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol; 4-chlorotetrafluorothiophenol; pentaiodothiophenol; 2-iodothiophenol; 3-iodothiophenol; 4-iodothiophenol; 2,3-iodothiophenol; 2,4-iodothiophenol; 3,4-iodothiophenol; 3,5-iodothiophenol; 2,3,4-iodothiophenol; 3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol; 2,3,5,6-tetraiodothiophenol; pentabromothiophenol; 2-bromothiophenol; 3-bromothiophenol 4-bromothiophenol; 2,3-bromothiophenol; 2,4-bromothiophenol; 3,4-bromothiophenol; 3,5-bromothiophenol; 2,3,4-bromothiophenol; 3,4,5-bromothiophenol; 2,3,4,5-tetrabromothiophenol; 2,3,5,6-tetrabromothiophenol; and their zinc salts, the metal salts thereof and mixtures thereof.

Outer core layer 215 may be formed by compression molding (vulcanization). Suitable vulcanization conditions may include a vulcanization temperature of between 130° C. and 190° C., and a vulcanization time of between 5 and 20 minutes. To obtain the desired rubber crosslinked body, the vulcanization temperature may be at least 140° C.

When outer core layer 215 of the present disclosure is produced by vulcanizing and curing the rubber composition in the above-described way, advantageous use may be made of a method in which the vulcanization step is divided into two stages: first, the outer core layer material may be placed in an outer core layer-forming mold and subjected to an initial vulcanization so as to produce a pair of semi-vulcanized hemispherical cups, following which a prefabricated inner core layer is placed in one of the hemispherical cups and is covered by the other hemispherical cup, in which state complete vulcanization is carried out.

The surface of inner core layer 220 placed in the hemispherical cups may be roughened before the placement to increase adhesion between inner core layer 220 and outer core layer 215. In some embodiments, the surface of inner core layer 220 may be pre-coated with an adhesive before placing inner core layer 220 in the hemispherical cups to enhance the durability of the golf ball and provide increased rebound.

Cover Layers

The thickness of the layers of golf ball 200 may be varied in order to achieve desired performance characteristics. In some embodiments, outer cover layer 205 may have a thickness of approximately 0.5 mm to 2 mm. In addition, in some embodiments, inner cover layer 210 may have a thickness of approximately 0.5 mm to 2 mm. In some embodiments, outer cover layer 205 and/or inner cover layer 210 may have a thickness of approximately 0.8 mm to 2 mm. In some embodiments, outer cover layer 205 and/or inner cover layer 210 may have a thickness of approximately 1 mm to 1.5 mm.

In some embodiments, inner cover layer 210 and/or outer cover layer 205 may be made from a thermoplastic material including at least one of an ionomer resin, a highly neutralized acid polymer, a polyamide resin, a polyester resin, and a polyurethane resin. In some embodiments, an ionomer resin, polyurethane resin, or highly neutralized acid polymer may be more preferred for inner cover layer 210 or outer cover layer 205. In some embodiments, inner cover layer 210 may be formed of the same type of material as outer cover layer 140. In other embodiments, inner cover layer 210 may be formed of a different type of material from outer cover layer 205.

In some embodiments, inner cover layer 130 may have a Shore D hardness, as measured on the curved surface, of at least 65. In some embodiments, outer cover layer 205 of golf ball 200 may have a Shore D hardness as measured on the curved surface in the range of about 45 to 60.

While various embodiments of the invention have been described, the description is intended to be exemplary, rather than limiting, and it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible that are within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents. Features of any embodiment described in the present disclosure may be included in any other embodiment described in the present disclosure. Also, various modifications and changes may be made within the scope of the attached claims. 

What is claimed is:
 1. A golf ball, comprising: a cover layer; an outer core layer disposed radially inward of the cover layer; and an inner core layer disposed radially inward of the outer core layer, the inner core layer having a first compression deformation at 24° C. and a second compression deformation at 70° C., wherein a first ratio between the second compression deformation and the first compression deformation is between approximately 1.5 and approximately 2.5.
 2. The golf ball according to claim 1, wherein after heating to 70° C. and cooling at 24° C. for 90 minutes, the inner core layer has a third compression deformation, wherein a second ratio between the third compression deformation and the first compression deformation is between approximately 1.08 and approximately 1.35.
 3. The golf ball according to claim 2, wherein after heating to 70° C. and cooling at 24° C. for 150 minutes, the inner core layer has a fourth compression deformation, wherein a third ratio between the fourth compression deformation and the first compression deformation is between approximately 1.08 and approximately 1.35.
 4. The golf ball according to claim 3, wherein after heating to 70° C. and cooling at 24° C. for 210 minutes, the inner core layer has a fifth compression deformation, wherein a fourth ratio between the fifth compression deformation and the first compression deformation is between approximately 1.08 and approximately 1.35.
 5. The golf ball according to claim 1, wherein the first compression deformation is between about 3 mm and about 5 mm.
 6. The golf ball according to claim 1, wherein the second compression deformation is between about 6 mm and about 8 mm.
 7. The golf ball according to claim 2, wherein the first compression deformation is between about 3 mm and about 5 mm.
 8. The golf ball according to claim 2, wherein the second compression deformation is between about 6 mm and about 8 mm.
 9. The golf ball according to claim 2, wherein the third compression deformation is between about 3.5 mm and 5.5 mm.
 10. The golf ball according to claim 8, wherein the third compression deformation is between about 3.5 mm and 5.5 mm.
 11. The golf ball according to claim 1, wherein the inner core layer is formed of a thermoplastic.
 12. The golf ball according to claim 11, wherein the thermoplastic is a highly neutralized acid polymer.
 13. The golf ball according to claim 6, wherein the second ratio is between approximately 1.13 and approximately 1.33.
 14. The golf ball according to claim 9, wherein the third ratio is between approximately 1.11 and approximately 1.26.
 15. The golf ball according to claim 4, wherein the fourth ratio is between approximately 1.09 and approximately 1.19.
 16. The golf ball according to claim 5, wherein the inner core layer has a diameter of approximately 24 mm.
 17. The golf ball according to claim 5, wherein the ratio is approximately 1.09 and the inner core layer has a diameter of approximately 28 mm. 